Electrical Puzzle

[Halmyre]

Replaced a ceiling light for my parents on Saturday - take down pendant, pu t up fancy new new three-bulb fixture, simple T&E, no spurs, loops or whate ver. Everything working AOK. Mum phones yesterday - switched on light, pop/ bang, all lights in flat go out. Contact breaker refuses to reset. Told her to switch all light switches off, try again - no joy. Told her to take all bulbs out of fixture - breaker still won't reset, which is kind of bafflin g, and also slightly worrying. I can only think that I put a screw through a cable (and I'm pretty sure I didn't), but why won't the breaker reset if the switch is off and all the bulbs are out, and why did it work OK at firs t?

[dr.s.lartius]

put up fancy new new three-bulb fixture, simple T&E, no spurs, loops or wha tever. Everything working AOK. Mum phones yesterday - switched on light, po p/bang, all lights in flat go out. Contact breaker refuses to reset. Told h er to switch all light switches off, try again - no joy. Told her to take a ll bulbs out of fixture - breaker still won't reset, which is kind of baffl ing, and also slightly worrying. I can only think that I put a screw throug h a cable (and I'm pretty sure I didn't), but why won't the breaker reset i f the switch is off and all the bulbs are out, and why did it work OK at fi rst?

You might enquire whether non-lights still work - vacuum cleaner, oven, fan heater, socketed stuff in general.

Is it the breaker which is instead one of the circuit fuses, or the breaker for a boxful of those? Does Economy 7 seem likely to work, if fitted?

[Tim Watts]

It's a "circuit breaker" not a contact breaker.

If there was a bang perhaps whatever caused the fault has further damaged the cable - maybe shorting neutral and earth which would prevent an RCBO[1] for resetting.

[1] Do you have ab MCB or RCBO? The latter will have a small test button as well as the main lever.

[John Rumm]

It could be there is a fault on the switched part of the circuit, and the switch contacts were welded together when it closed the fault current the first time. It may turn off mechanically but not electrically.

Faulty MCB is another possibility.

Or there may be an (possibly unrelated) fault elsewhere on the circuit.

That's harder to guess at!

You can test the fault after the switch conjecture by disconnecting one of the wires at the switch, and see if the MCB resets then.

You can test the knackered MCB option by disconnecting the live out from it in the CU.

If the first mod does not fix it, and the second does, then you have the fault elsewhere situation to deal with.

[Halmyre]

, put up fancy new new three-bulb fixture, simple T&E, no spurs, loops or w hatever. Everything working AOK. Mum phones yesterday - switched on light, pop/bang, all lights in flat go out. Contact breaker refuses to reset. Told her to switch all light switches off, try again - no joy. Told her to take all bulbs out of fixture - breaker still won't reset, which is kind of baf fling, and also slightly worrying. I can only think that I put a screw thro ugh a cable (and I'm pretty sure I didn't), but why won't the breaker reset if the switch is off and all the bulbs are out, and why did it work OK at first?

an heater, socketed stuff in general.

er for a boxful of those? Does Economy 7 seem likely to work, if fitted?

Just the lights, everything else was fine.

[Halmyre]

Ta, sadly I don't live near enough to pop over to investigate it, just curious as to the possible causes. Peeved because I've done a fair bit of similar work between my own house, sister-in-laws and parent's without any problems to date.

Parents are going to get a real electrician in to look at it, who will no doubt tut, suck his teeth, shake his head and say "dear oh dear, what cowboy put this in, bleedin' amateurs", etc...

[Brian Gaff]

Probably something totally unrelated unless there was a crucial cable somewhere near where you did put a screw in. Iit has to be one though that is unswitched as you say.

Brian

[Brian Gaff]

I'd imagine a cable above the fitting that in fact feeds the whole circuit in the flat from the breaker. If a screw went partly through that cable, say in the void above the ceiling, then it might take a while for it to in fact finally short out and blow the fuse. It will be a real pain to get at and fix if it is in such a daft place though, as a hole in the ceiling will be needed for a connection block of some kind.

Another thought of course is that with unswitched lives in roses these days, if that wire was not secured in the rose very well and its somehow sprung and touched something earthy or neutrally, if that is a word, then bang. Lets hope its the latter as that will be easier to see and fix. Brian

[harry]

put up fancy new new three-bulb fixture, simple T&E, no spurs, loops or wha tever. Everything working AOK. Mum phones yesterday - switched on light, po p/bang, all lights in flat go out. Contact breaker refuses to reset. Told h er to switch all light switches off, try again - no joy. Told her to take a ll bulbs out of fixture - breaker still won't reset, which is kind of baffl ing, and also slightly worrying. I can only think that I put a screw throug h a cable (and I'm pretty sure I didn't), but why won't the breaker reset i f the switch is off and all the bulbs are out, and why did it work OK at fi rst?

At the ceiling rose (ie the bit attached to the ceiling) there may well be three terminals; live, neutral and switch wire. You may have shorted out live and neutral.

The abovementioned live is permanently live regardless of switch position B TW.

[Halmyre]

put up fancy new new three-bulb fixture, simple T&E, no spurs, loops or wha tever. Everything working AOK. Mum phones yesterday - switched on light, po p/bang, all lights in flat go out. Contact breaker refuses to reset. Told h er to switch all light switches off, try again - no joy. Told her to take a ll bulbs out of fixture - breaker still won't reset, which is kind of baffl ing, and also slightly worrying. I can only think that I put a screw throug h a cable (and I'm pretty sure I didn't), but why won't the breaker reset i f the switch is off and all the bulbs are out, and why did it work OK at fi rst?

Update - yep, I'd snagged a wire while I was securing the fitting to its ba se plate. In my defence it looked (to me at least) like there was twice as much wire in the fitting as was necessary. :(

However, after the sparky who came out to fix the fault had left, mum found out that the switch wouldn't turn the lights off! - she says it feels 'odd ', so it sounds like the switch is borked. Can't believe the bloke didn't a ctually check the switch.

[MrCheerful]

There is always going to be the last occasion that something works, like a light bulb, anything can fail at any moment.

[Halmyre]

t, put up fancy new new three-bulb fixture, simple T&E, no spurs, loops or whatever. Everything working AOK. Mum phones yesterday - switched on light, pop/bang, all lights in flat go out. Contact breaker refuses to reset. Tol d her to switch all light switches off, try again - no joy. Told her to tak e all bulbs out of fixture - breaker still won't reset, which is kind of ba ffling, and also slightly worrying. I can only think that I put a screw thr ough a cable (and I'm pretty sure I didn't), but why won't the breaker rese t if the switch is off and all the bulbs are out, and why did it work OK at first?

s base plate. In my defence it looked (to me at least) like there was twice as much wire in the fitting as was necessary. :(

ound out that the switch wouldn't turn the lights off! - she says it feels 'odd', so it sounds like the switch is borked. Can't believe the bloke didn 't actually check the switch.

GU10 bulbs. They're like buses, work for a while then they all start failin g at once. Or it's like dead celebrities, always go in threes...

[Dave Plowman (News)]

If it is wired with the switch drop from the fitting to the wall, it's likely he's wired it to the wrong terminal.